Polymer compound, resist composition and dissolution inhibitor agent containing the polymer compound

ABSTRACT

Provided are a polymer compound having high transparency for use in a photoresist composition for microfabrication of the next generation, a resist composition using the polymer compound as a base polymer, and a dissolution inhibitor agent composed of the polymer compound. 
     To ensure etching resistance, an alicyclic group is introduced into a side chain portion. Hydrogen atoms on the ring of the alicyclic group are highly fluorinated to ensure transparency to light of 157 nanometer wavelength, represented by an adsorption coefficient equal to or less than 3.0 μm −1 . As the alicyclic group, a polycyclic group is preferably used. Hydrogen atoms are highly fluorinated by preferably substituting all hydrogen atoms on the ring by fluorine atoms, that is, forming a perfluoroalicyclic group. The resist composition is formed by using the polymer compound as a base polymer and further, the dissolution inhibitor agent is formed of the polymer compound.

TECHNICAL FIELD

The present invention relates to a polymer compound excellent intransparency suitable as a resin compound, which becomes soluble orinsoluble in alkali in response to acid, used, for example, as the basepolymer of a chemical amplification type resist composition for use inlithographic patterning of a semiconductor integration circuit, and adissolution inhibitor agent optionally added to the resist composition,and also relates to a resist composition and a dissolution inhibitoragent using the polymer compound as a resin component.

BACKGROUND ART

It is no exaggeration to say that miniaturization of a semiconductorintegrated circuit pattern has been attained by the progress ofphotolithography and peripheral technologies. The photolithography, asknown well, is supported by roughly two techniques: one is a techniqueregarding the wavelength of the applied light and the number of openingsof a reduced projection light exposure apparatus called a stepper, andthe other is a technique regarding resist properties, mainly theresolution of a photoresist composition onto which a mask pattern is tobe transferred by the stepper. These two techniques have worked witheach other, like two wheels of a car, to improve the accuracy ofphotolithographic pattern-processing of a semiconductor integratedcircuit.

The wavelength of a light source-used in a stepper has been made shorterand shorter in order to satisfy the requirement for higher resolution ofa circuit pattern. To obtain a resist resolution of about 0.5micrometers, generally use is made of a “g” line of a mercury lamphaving a main spectrum at 436 nanometers and to obtain a resistresolution of about 0.5 to 0.30 micrometers, use is made of an “i” lineof a mercury lamp having a main spectrum at 365 nanometers. Furthermore,to obtain a resist resolution of about 0.30 to 0.15 micrometers, KrFexcimer laser of 248 nanometers is used. To obtain a resist resolutionof about 0.15 micrometers or less, ArF excimer laser light of 193nanometers is used. For further reduction, use of F₂ excimer laser lightof 157 nanometers and Ar₂ excimer laser light of 126 nanometers, hasbeen studied.

On the other hand, in view of a photoresist composition, variousattempts have been made including the combination of a photoresistcomposition with an organic or inorganic reflection protecting film, andcontrivance of illumination systems. By virtue of these attempts,lithography using KrF excimer laser light has been still in use andtherefore a KrF photoresist prolongs its life at the present time. Morespecifically, a KrF photoresist composition has been developed with awavelength of λ/2 or less, about 110 nanometers, in view. Also in thelithography using ArF excimer laser light, it has been desired todevelop an ArF photoresist composition suitable for a large-scaleproduction of a future design for about not more than 90 nanometer node.Furthermore, the lithography using F₂excimer laser light has receivedattention because it can realize future microfabrication of about 65nanometers or less. Therefore, the development of a photoresistcomposition has been proceeding for sufficiently attaining thelithographic microfabrication using F2 excimer laser light.

As is well known, in the lithography, short-wavelength light is appliedto a photoresist layer coated on a laminated semiconductor substrate viaa mask having a negative pattern or a positive pattern of a desiredsemiconductor integrated circuit (light exposure). The photoresist layercontains a photosensitive polymer as a main component, which reacts withirradiated light to become insoluble (negative) or soluble (positive) inalkali. After pattern light exposure, the resist layer is subjected to apost exposure baking step to secure the reaction of the resist layercaused by light exposure. Subsequently, the resist layer is developed toremove a soluble portion. As a result, a photoresist pattern layer whichaccurately reflects the desired circuit pattern is formed on thelaminated semiconductor substrate. Thereafter, in some cases, thepatterned photoresist layer is subjected to a post baking step tosufficiently cure it in order to give resistance to the followingetching step. In the etching step, using the patterned photoresist layeras a mask, the surface layer or the upper layer of the laminatedsemiconductor substrate is dry-etched along the pattern.

Therefore, the most important property required for a photoresistcomposition is to provide good resolution. To attain this, patterninglight (applied light) must reach not only the surface portion of aresist layer but also the bottom portion near the substrate, therebyallowing light to sufficiently reach the bottom portion of theirradiated resist layer. In other words, the resist layer must have“transparency to irradiation light”.

As is well known, to satisfy the requirements for the lithographicmicrofabrication as mentioned above, chemical amplification-type resistcompositions have been used primarily in recent years. The chemicalamplification-type resist composition contains at least a polymercompound having a group highly reactive to acid, an acid generatingagent generating acid upon light exposure, and a solvent dissolvingthem. When the coating film of the resist composition is exposed topatterning light, acid is released from the acid generating agentpresent in the exposed portion and reacts with the base polymer (polymercompound mentioned above) present in the light exposure portion. In apositive resist composition, the base polymer becomes soluble in alkalisince a protecting group (also called as acid-dissociable dissolutionsuppressing group) is removed from the base polymer by the catalyticaction of the acid. Therefore, when the resist layer having a latentimage is partially developed by using an alkaline developing solution, apositive-type resist pattern to the mask pattern can be obtained. On theother hand, in a negative resist composition which uses a polymersoluble in a developing solution, the light exposure portion becomesinsoluble in the developing solution by the catalytic action of theacid. To the chemical amplification type resist composition, anotherpolymer component serving as a dissolution inhibitor agent may beoptionally added. The dissolution inhibitor agent is a polymer having arelatively lower molecular weight of 5,000 or 3,000 or less. Thedissolution inhibitor agent, from which a protecting group is removed byan acid generated from an acid generating agent, increasing itssolubility in an alkaline developing solution. In other words, thedissolution inhibitor agent suppresses the portion of the resist filmremaining as an insoluble portion (non light-exposure portion) frombeing dissolved in the alkaline developing solution and simultaneouslyaccelerates dissolution of a soluble portion (light exposure portion) bythe alkaline developing solution.

To improve the transparency of a chemical amplification type resistcomposition to light applied thereto, a base polymer and an optionallyadded polymer serving as a dissolution inhibitor agent must be composedof a polymer compound exhibiting high transparency of the applied light.

The resin components such as the base polymer and dissolution inhibitoragent of a resist composition to be used in the lithography by F₂excimer laser light, which is a light source of the next generationstepper, must have high transparency to the main spectrum (157nanometers) of the F₂ excimer laser light. A desired transparency of theresist film to light having a wavelength of 157 nanometers is disclosedfor example in M. K. Crawford et al., “New material for 157 nanometersPhotoresists: Characterization and Properties”, Proceedings of SPIE,Vol. 3999 (2000), pp357 to 364. This document reveals that theabsorption coefficient (optical coefficient) of a resist film(normalized in thickness) must be equal to or less than 3.0 (μm⁻¹) toobtain a sufficient pattern transfer resolution.

In contrast, a conventional resist material absorbs light having awavelength of 157 nanometers. In other words, the transparency of theconventional resist material to the applied light having a wavelength of157 nanometers is low. This means that it is impossible to obtain thenext generation resist composition based on the conventional resistmaterials.

As described above, in the technical field of providing photoresistcompositions, it has been investigated to develop a polymer compoundhaving high transparency to light having a wavelength of 157 nanometers.Up to the present, fluorine (F) and silicon (Si) are introduced to apolymer compound to attain the transparency to applied light having themain spectrum at a wavelength of 157 nanometers. Based on this, a novelpolymer having not only the transparency but also good resistperformances, such as alkaline solubility determining the developingcharacteristics after light exposure, pattern transfer resolution, andetching resistance, has been developed. However, as to how manypercentages of fluorine and silicon-should be introduced, which part ofa polymer molecule they should be introduced, and which components ofthe polymer they should be introduced have not yet been clarified inorder to improve the transparency to applied light to a desired level ormore while maintaining other characteristics such as dry-etchingresistance.

As base polymers for resist compositions having transparency to an ArFexcimer laser light, the following polymers are conventionally known: acopolymer of an acrylic ester monomer having an alicyclic groupstructure and a δ-lactone structure linked to and an androsteronderivative, for example, disclosed in Japanese Patent ApplicationLaid-Open No. 2001-174993; a polymer of a polycyclic unsaturatedhydrocarbon derivative which is obtained by subjecting an acrylic acidhaving an electron-withdrawing substituent at the a position andcyclopentadien or dicyclopentadien to the Diels-Alder reaction to obtaina polycyclic unsaturated carboxylic acid, followed by substituting ahydrogen atom of a hydroxyl group of the unsaturated carboxylic acid byan acid dissociable dissolution suppressing group, for example,disclosed in Japanese Patent Application Laid-Open No. 2001-328964; acopolymer having a monomeric unit derived from an alicyclic hydrocarbonhaving a polymeric carbon-carbon double bond in the alicyclic ring and amonomeric unit derived from (meta) acrylonitirile, for example,disclosed in Japanese Patent Application Laid-Open No. 2002-196495; apolymer having a monomer having a lactone structure combined to a vinylgroup as a monomeric unit, for example, disclosed in Japanese PatentApplication Laid-Open No. 2002-278069; and a copolymer of acrylic estermonomer having a fluorine atom at the a position and a vinyl etherderivative, for example, disclosed in Japanese Patent ApplicationLaid-Open No. 2002-293840. In the copolymer disclosed in Japanese PatentApplication Laid-Open No. 2001-174993, a fluorine atom is not introducedto improve the transparency. In the polymer disclosed in Japanese PatentApplication Laid-Open No. 2001-328964, fluorine is introduced partly ina monomeric unit or in a side chain ring; however, the relationshipbetween the fluorine introduction and the transparency is not clear. Inthe copolymer disclosed in Japanese Patent Application Laid-Open No.2002-196495, fluorine is introduced in a part of a terminal-endprotecting group of a side chain ring; however, the relationship betweenthe fluorine introduction and the transparency is not clear. In thepolymer disclosed in Japanese Patent Application Laid-Open No.2002-278069, fluorine is not introduced to improve the transparency. Inthe copolymer disclosed in Japanese Patent Application Laid-Open No.2002-293840, a copolymer in which part or the about half of hydrogenatoms on a side chain ring are substituted by fluorine atoms isexemplified; however, the relationship between the substitution and thetransparency is not clear.

As described above, various polymer compounds have been proposed up topresent to improve the transparency to the applied light having awavelength of 200 nanometers or less. However, it has not yet beenelucidated as to which formula of a polymer fluorine should beintroduced, which part of the polymer molecule fluorine should beintroduced, and how many percentages of fluorine should be introducedhave not yet been clarified in order to improve the transparency tolight to a desired level or more while maintaining other characteristicssuch as dry-etching resistance.

DISCLOSURE OF THE INVENTION

The present invention has been achieved in order to solve the aboveproblems. It is an object of the invention is to provide a polymercompound having high transparency for use in a photoresist compositionfor the microfabrication of the next generation, and a resistcomposition and a dissolution inhibitor agent having the polymercompound, and more specifically, to provide a polymer compound havingthe transparency represented by an absorption coefficient equal to orless than 3.0 μm⁻¹ to the applied light having a wavelength of 157nanometers, a resist compound containing the polymer compound as a basepolymer and a dissolution inhibitor agent consisted by the polymercompound.

The present inventors conducted intensive studies to overcome theaforementioned problems. As a result, they found that the transparencyrepresented by an absorption coefficient equal to or less than 3.0 μm⁻¹to the applied light having a wavelength of 157 nanometers can beobtained by introducing an alicyclic group into a side chain portion ofthe polymer, thereby ensuring etching resistance, and simultaneouslysubstituting more than half number of hydrogen atoms on the ring of thealicyclic group by fluorine atoms. Furthermore, they found that apolycyclic group is preferably used as the alicyclic group and thathigh-level fluorine substation is desirably attained by substituting allhydrogen atoms on the ring by fluorine atoms, in other words, by forminga perfluoroalicyclic group.

It is an object of the present invention is to provide a polymercompound. The polymer compound according to the present invention is onehaving a monomeric unit which has an alicyclic group in a side chain andcharacterized in that the alicyclic group is highly fluorinated and hastransparency represented by an absorption coefficient equal to or lessthan 3.0 μm⁻¹ to light having a wavelength of 157 nanometers.

It is another object of the present invention is to provide a resistcomposition. The resist composition of the present invention includesthe polymer compound mentioned above. The resist composition may containthe polymer compound as a base polymer or as a dissolution inhibitoragent optionally added, or may contain both. However, when it is used asthe base is polymer of a resist composition, the polymer compound has aweight-average molecular weight of 1,000 to 20,000, preferably 3,000 to20,000. When used as a dissolution inhibitor agent, the polymer compoundpreferably has a weight-average molecular weight of 1,000 to 5,000.

As described above, the polymer compound according to the presentinvention is one having a monomeric unit which has an alicyclic group ina side chain and characterized in that the alicyclic group is highlyfluorinated and has transparency represented by an absorptioncoefficient equal to or less than 3.0 μm⁻¹ to light having a wavelengthof 157 nanometers. Such a polymer compound can be expressed by generalformula (1):

where n is an integer; X is an ester group of carboxylic acid,

ether group (—O—), —CH₂—O—, or an alkylidene group,

Z enclosed by a circle is a highly fluorinated alicyclic group,preferably, a polycyclic group; R¹, R², R³, R⁵, R⁶ and R⁷ areindependently one selected from the group consisting of a hydrogen atom,lower alkyl group, fluorine atom, and fluorinated lower alkyl group; Iis an integer of 0 to 3; and R⁴ is a hydroxyl group.

In the general formula (1), the alicyclic group represented by circled Zis preferably an adamantyl group as a tricyclic alicyclic hydrocarbongroup. It is desirable that the hydrogen atoms on the ring of alicyclicgroup are mostly fluorinated, and more desirable that the alicyclicgroup is a perfluoroadamrantyl group.

BEST MODE FOR CARRYING OUT THE INVENTION

As described above, the polymer compound according to the presentinvention is one having a monomeric unit containing an alicyclic groupin a side chain, in which the alicyclic group is highly fluorinated, andhaving transparency represented by an absorption coefficient equal to orless than 3.0 μm⁻¹ to the applied light having a wavelength of 157nanometers.

In such a construction, the alicyclic group is desirable that allhydrogen atoms on the ring are fluorinated. However, when a hydrophilicsubstituent (e.g., hydroxyl group) other than a hydrogen atom is presenton the ring, the substituent is not fluorinated. In addition, thealicyclic group is desirably a polycyclic group.

The alicyclic group may contain a hydrophilic group. Because of thepresence of a hydrophilic group, it is expected that, when the polymercompound is used as the base polymer and a dissolution inhibitor agentof a resist composition, the adhesion property of a resist film and aresist pattern to a substrate can be improved.

As the alicyclic group, an alicyclic group of an ArF resist may be used.In particular, as a polycyclic group, any one of known polycyclic groupsmay be used. Examples of the alicyclic groups include groups obtained byremoving a single hydrogen atom from bicycloalkane, tricycloalkane, andtetracycloalkan, more specifically, groups obtained by removing a singlehydrogen atom from polycycloalkanes such as adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane. Among them, anadamantyl group, norbornyl group, and tetracyclododecanyl group arepreferable in an industrial point of view. Particularly, an adamantylgroup is preferable. An adamantyl group exhibits high transparency tonot only light of not more than 300 nanometer wavelength but also lightof not less than 300 nanometer wavelength and therefore more widely andpreferably used in a resist composition.

As the monomeric unit, a unit derived by cleavage of an ethylenic doublebond such as acrylic ester or metacrylic ester, vinyl ether, or allylether may be preferably used.

Furthermore, the polymer compound according to the present invention ispreferably a copolymer; in other words, may have a second monomericunit. If the second monomeric unit is contained, a substituent having asensitivity to acid can be linked to the second monomeric unit. Byvirtue of this, alkaline solubility or alkaline insolubility can becontrolled by an acid catalytic function of the polymer thus imparted tothe second monomeric unit, thereby improving the degree of freedom indesigning sensitivity to the acid catalyst. More specifically, thesecond monomeric unit may have an acid dissociating group and aninsoluble group in acid.

Furthermore, as the second monomeric unit, a monomeric unit derived fromacrylic ester or metacrylic ester and a monomeric unit derived bycleavage of an ethylenic double bond such as tetrafluoroethylene maypreferably be used.

As an acrylic ester or metacrylic ester prefereably used as a monomericunit, for example, compounds having the following structures may bementioned.

Furthermore, as vinyl ether preferably used as a monomeric unit, forexample, a compound having the following structure may be mentioned.

As an allyl ether preferably us ed an a monomeric unit, a group havingthe following structure may be used.

Specific examples of a polymer having a monomeric unit containing anadamantly group suitable as an alicyclic group include1-perfluoroadamantyl methacrylate having a monomeric unit represented bygeneral formula (2) and a polymer having a monomeric unit derived from3-hydroxy-1-perfluoroadamantyl acrylate having a monomeric unitrepresented by general formula (3). Note that, m and n in the formulabelow are integers.

1-perfluoroadamantyl metacrylate and 3-hydroxy-1-perfluoroadamantylacrylate may be obtained generally by the following synthetic method, asan example. After 1 equivalent of 1-hydroxylperfluoroadamantane orperfluoroadamantanediol and 1.2 equivalents of triethylamine aredissolved in diethyl ether, 1 equivalent of chloride acrylate orchloride metacrylate is added slowly and dropwise to the resultantsolution under ice cooling. After completion of the reaction, water isadded to the reaction solution and extracted with diethyl ether. Theorganic layer obtained is dried over magnesium sulfate. After magnesiumsulfate is filtered off, the obtained diethyl ether solution wasconcentrated and subjected to column-chromatographic separation toobtain 1-perfluoroadamantyl (meta)acrylate or3-hydroxy-1-perfluoroadamantyl (meta)acrylate. If these monomers areobtained, a polymer compound having each of the monomers as a unit canbe obtained by a radical polymerization method or the like using a knownpolymerization initiation agent such as azobisisobutyronitrile (AIBN).

Furthermore, as an example of a compound having a monomeric unit derivedfrom a preferable acrylic ester or a metacrylic ester as a secondmonomeric unit, groups having the following structures may be mentioned.

Furthermore, as a compound having a monomeric unit derived by cleavageof another vinylic double bond suitable as a second monomeric unit,those having the following structures may be mentioned.

In addition to this, a fluorine-containing monocyclic monomeric unitdisclosed in Japanese Patent Application Laid-Open No. 2002-90997 may beused. The fluorine-containing monocyclic polymer disclosed in JapanesePatent Application Laid-Open No. 2002-90997 is one including a repeatunit of a cyclic structure formed through a cyclization reaction betweena monomer unit of a diene system monomer (a), which is composed of acompound lo represented by CH₂═CH—Y—CH═CH₂, or a derivative thereof, anda monomer unit of a fluorine-containing vinyl monomer (b); and aprotected acidic group derived from, a fluorine-containing vinylmonomer. In the aforementioned formula, Y represents a methylene groupor an oxygen atom. Examples of the derivative of (a) include compoundshaving an alkyl-group substituent and a hydroxide-group substituent,where the alkyl-group substituent is preferably a lower alkyl grouphaving 1 to 4 carbon atoms. These second monomeric units must have anacid dissociable dissolution suppressing group when they are used as apositive resist, whereas they must have an insoluble group in acid whenthey are used as a negative resist. Furthermore, to enhance theadhesiveness between a substrate and a resist pattern, a monomeric unithaving a γ-butyrolactone group may be used. To further improvetransparency, a compound of the present invention such astetrafluoroethylene may be used. If necessary, these compounds may beappropriately used in a combination of two or more elements to obtain atertiary, quaternary, or quinary copolymer. Note that specific examplesof the structure of a polymer compound according to the presentinvention are as follows:

Furthermore, as the acid dissociable dissolution suppressing group, anygroup may be used as long as it has been proposed as an acid dissociabledissolution suppressing group in a chemical amplification type positiveresist; however, particularly one formed of a tertiary alkyl group maybe used. Specific examples of the tertiary alkyl group include thoseformed of a chain alkyl group, such as tert-butyl group and tert-amylgroup or the like, and those formed of a cyclic alkyl group and a chainalkyl group, such as a 2-methyl-2-adamantyl group, and a2-ethyl-2-adamantyl group or the like.

Furthermore, as the insoluble group in acid, a hydroxycarbonic acid suchas δ-hydroxycarbonic acid disclosed in Japanese Patent ApplicationLaid-Open No. 2001-174993, from which a lactone can be produced by theaction of an acid, may be mentioned.

A polymer compound according to the present invention contains amonomeric unit having a highly fluorinated alicyclic group as describedabove, and more preferably, contains the monomeric unit and a secondmonomeric unit. The polymer compound may be used as not only the basepolymer but also the dissolution inhibitor agent of a chemicalamplification resist. When the polymer compound is used as thedissolution inhibitor agent, as is the case where the polymer compoundis used as the base polymer for a positive resist, it must contain anacid dissociable dissolution suppressing group having a weight—averagemolecular weight of about 2,000 to 5,000. The dissolution inhibitoragent may be used in combination with a polymer compound according tothe present invention or another known base polymer.

A polymer compound according to the present invention may be easilyproduced by a known polymerization method, typically by a radicalpolymerization. A polymer compound is produced by dissolving a requisitemonomer in a solvent, for example, tetrahydrofuran, ethyl acetate,methylisobutylketone or methylethylketone or the like, and adding aradical polymerization initiating agent to the resultant solution,followed by heating.

Examples of the polymerization initiating agent includeazobisisobutyronitrile (AIBN)(application temperature: 60 to 90° C.),2,2′-azobis-(2,4-dimethyl valeronitrile (application temperature: 45 to70° C.), 2,2′-azobis-(2-methyliso butyronitrile (applicationtemperature: 60 to 95° C.), tert-butylperoctoate (applicationtemperature: 75 to 100° C.), 1,1′-azobis-(cyclohexane-1-carbonitirile)(application temperature: 80 to 110° C.), and1-[(1-diazo-1-methylethyl)azo]formamide (application temperature: 95 to120° C.) or the like, and which may be used singly or in combination. Inparticular, AIBN is preferably used as a general polymerizationinitiation agent.

Thereafter, a reaction solution containing the polymer compound thusobtained is added dropwise to a large volume of poor solvent such asisopropanol, methanol, water, n-heptane, or n-hexane or the like toprecipitate the polymer compound. Thereafter, the obtained precipitateis filtrated and dried to obtain the polymer compound according to thepresent invention (resin). This precipitation step, even though it isnot required in some cases, is useful to remove a monomer and apolymerization initiation agent remaining unreacted in a reactionsolution. If an unreacted monomers and polymerization initiation agentremain as they are, they may negatively affect the performance of aresist, so that it is preferable to remove them. Furthermore, to preparea resist composition, a component serving as an acid generating agentmust be blended together in the composition.

As an acid generating agent to be used in the resist compositionaccording to the present invention, any agent may be used as long as itis appropriately selected from known acid generating agents for use inchemical amplification type resists.

Examples of the acid generating agent include onium salts such asdiphenyl iodonium trifluoromethanesulfonate, (4-methoxyphenyl)phenyliodonium trifluoromethanesulfonate, bis(p-tert-butylphenyl) iodoniumtrifluoromethanesulfonate, triphenyl sulfoniumtrifluoromethanesulfonate, (4-methoxyphenyl)diphenyl sulfoniumtrifluoromethanesulfonate, (4-methylphenyl)diphenyl sulfoniumnonafluorobutanesulfonate, (p-tert-butylphenyl)diphenyl sulfoniumtrifluoromethanesulfonate, diphenyl iodonium nonafluorobutanesulfonate,bis(p-tert-butylphenyl) iodonium nonafluorobutanesulfonate, andtriphenylsulfonium nonafluorobutanesulfonate or the like. Among them, anonium salt containing fluoroalkylsulfonate ion as an anion ispreferable.

As the acid generating component, a single acid generating agent may beused alone or two or more acid generation agents may be used incombination.

The amount of an acid generating agent to be used is 0.5 to 30 parts byweight, preferably 1 to 10 parts by weight based on the amount of thebase polymer as 100 parts. If the amount is less than 0.5 parts byweight, pattern formation is not performed sufficiently. On the otherhand, if the amount exceeds 30 parts by weight, a homogeneous solutionis hardly obtained, with the result that storage stability may decrease.

A resist component according to the present invention can be produced bydissolving the base polymer and the acid generating agent, andoptionally, the dissolution suppressing agent and an arbitrary component(described later) in an organic solvent.

As the organic solvent, any organic solvent may be used as long as itcan dissolve each of the components mentioned above to make ahomogeneous solution and may be appropriately selected from knownsolvents for use in chemical amplification resists and used singly or inadmixture with two or more solvents.

Examples of the organic solvent include ketones such as acetone,methylethyl ketone, cyclohexanone, methylisoamyl ketone, and 2-heptanoneor the like; polyalcohols and derivatives thereof such as a monomethylether, monoethyl ether, monopropyl ether, monobutyl ether or monophenylether or the like of ethylene glycol, ethylene glycol monoacetate,diethylene glycol, diethylene glycol monoacetate, propylene glycol,propylene glycol monoacetate, dipropylene glycol, and dipropylene glycolmonoacetate or the like; cyclic ethers such as dioxane; and esters suchas methyl lactate, ethyl is lactate, methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate or the like. These organicsolvents may be used singly or in admixture with two or more members.

Among them, propylene glycol monomethyl ether acetate (PGMEA) andpropylene glycol monomethyl ether (PGME) may be preferably used.Furthermore, it is preferable that these solvents are mixed with polarsolvents having a hydroxyl group and lactone such as ethyl lactate (EL)and γ-butyro lactone or the like. This is because the storage stabilityof a resist composition can be improved.

A resist composition according to the present invention may contain aknown amine component, preferably, a secondary lower aliphatic amine ora tertiary lower aliphatic amine, as an optional component, in order tostabilize a resist pattern and stabilize storage with time.

The term “lower aliphatic amine” refers to an amine of an alkyl andalkylalcohol having equal to or less than 5 carbon atoms. Examples ofthe secondary and tertiary amines include trimethylamine, diethylamine,triethylamine, di-n-propylamine, tri-n-propylamine, tripentylamine,diethanolamine, and triethanolamine or the like. Among them,particularly, alkanolamine such as triethanolamine is preferable.

These amines may be used singly or in admixture with two or moremembers. These amines may be used in an amount of 0.01 to 1 part byweight based on the amount of the base polymer component.

To the resist composition according to the present invention, a miscibleadditive may be further added if desired. Examples of such a miscibleadditive include an additional resin for improving the performance of aresist film, a surfactant for improving coating ability, dissolutionsuppressing agent, plasticizer, stabilizer, coloring agent, and halationpreventing agent or the like.

(Pattern formation method)

A method of forming a resist pattern will be described next.

First, a resist composition according to the present invention isapplied onto a substrate such as a silicon wafer or the like by aspinner or the like and subjected to prebaking. Subsequently, thecoating film of the resist composition is selectively exposed to lightthrough a desired mask pattern by means of light exposure apparatus, andthereafter, subjected to post-exposure baking (PEB). Subsequently, thecoating film is developed with an alkaline developing solution andrinsed with pure water. By a series of treatments, the coating film ofthe resist composition is patterned in accordance with the mask patternto obtain a resist pattern.

The wavelength of light to be applied is not particularly limited. ArFexcimer laser, KrF excimer laser, F₂ excimer laser, extreme ultra violet(EUV) light, vacuum ultra violet (VUV) light, electron beam, andradioactive rays such as X-rays and soft X-rays or the like may be used.In particular, the resist composition according to the present inventioneffectively works in response to F₂ excimer laser.

Note that an anti-reflection film formed of an organic or inorganicmaterial may be formed between the substrate and the coating film of aresist composition.

The polymer compound according to the present invention may be amonopolymer having a highly fluorinated monomeric unit having analicyclic group at a side chain or a copolymer with a second monomericunit. In the case of a copolymer, the amount of a first monomeric unitmay fall within the range of 5 to 40% by mole, preferably 10 to 35% bymole, whereas the amount of a second monomeric polymer may fall withinthe range of 60 to 95% by mole, preferably 65 to 90% by mole. The secondmonomeric unit may be used in admixture of two or more members.

EXAMPLES

The present invention will be explained by way of examples, which areused for more preferably illustrating the present invention, but notintended to limit the present invention.

Resin Synthesis Example 1

First, 5.0 grams of 1-perfluoroadamantyl methacrylate was dissolved in20 milliliters of tetrahydrofuran and further 0.1 gram ofazobisisobutyronitrile was added. After heating at 70° C. for 5 hoursunder reflux, the resultant solution was added dropwise to 500milliliters of methanol. The precipitated resin was filtered off, anddried under reduced pressure to obtain a white powdery resin. The resinwas a polymer compound having a monomeric unit represented by thegeneral formula (2) mentioned above. The yield of the resin was 1 gram.The weight-average molecular weight (Mw) of the resin was 8,000 and thedegree of dispersion (Mw/Mn) was 1.6. Hereinafter, the resin will bereferred to as Resin 1.

Resin Synthesis Example 2

First, 10.0 grams of 3-hydroxy-1-perfluoroadamantyl acrylate wasdissolved in 50 milliliters of tetrahydrofuran and further 0.1 gram ofazobisisobutyronitrile was added. After heating at 70° C. for 5 hoursunder reflux, the resultant solution was added dropwise to 1 liter ofn-heptane. The precipitated resin was filtered off, and dried underreduced pressure to obtain a resin. The resin was a polymer compoundhaving a monomeric unit represented by the general formula (3) mentionedabove. The yield of the resin was 5.1 grams. The weight-averagemolecular weight (Mw) of the resin was 4,800 and the degree ofdispersion (Mw/Mn) was 1.28. Hereinafter, the resin will be referred toas Resin 2.

Resin Synthesis Example 3

First, 4.40 grams of 2-methyl-2-adamantyl acrylate, 3.12 grams ofγ-butyrolactone acrylate, and 4.74 grams of 3-hydroxyperfluoroadamantylacrylate were dissolved in 50 milliliters of tetrahydrofuran, andfurther 0.61 grams of azobisisobutyronitrile was added. After heating at70° C. for 5 hours under reflux, the resultant solution was addeddropwise to 1 liter of n-heptane. The precipitated resin was filteredoff, and dried under reduced pressure to obtain a resin. The resin was apolymer compound having three types of monomeric units representedrespectively by general formulas (4), (5) below and the general formula(3) mentioned above. The yield of the resin was 7.0 grams. Theweight-average molecular weight (Mw) of the resin was 5,100 and thedegree of dispersion (Mw/Mn) was 2.37. Hereinafter, the resin will bereferred to as Resin 3. Note that, in general formulas (4) and (5)below, p and q are integers. The obtained polymer compound is useful asthe base polymer of a positive type resist and a dissolution inhibitoragent.

Resin Synthesis Example 4

First, 2.8 grams of a lactone monomer and 2.4 grams of 3-hydroxyperfluoroadamantyl acrylate were dissolved in 90 milliliters oftetrahydrofuran, and further 0.15 grams of azobisisobutyronitrile wasadded. After heating at 70° C. for 5 hours under reflux, the resultantsolution was added dropwise to 1 liter of n-heptane. The resultant solidmatter was filtrated, and dried at 40° C. for 3 hours under vacuum. 3.0g of the obtained resin was dissolved in 100 milliliters oftetrahydrofuran and 110 grams of tetramethyl ammonium hydroxide (TMAH)was added. After the solution mixture was stirred at room temperaturefor 6 hours, the mixture was neutralized with 0.04N of HCl. Thehydrolyzed resin was extracted with ethyl acetate. The organic layer waswashed with pure water and added dropwise to 1 liter of n-heptane. Theprecipitated resin was filtrated off and dried at 30° C. for 2 hoursunder vacuum to obtain a resin. The resin was a polymer compound havingtwo types of monomeric units represented respectively by general formula(6) below and the general formula (3) mentioned above. The yield of theresin was 1.5 grams. The weight-average molecular weight (Mw) of theresin was 1,200 and the degree of dispersion (Mw/Mn) was 1.79.Hereinafter, the resin will be referred to as Resin 4. Note that, ingeneral formula (6) below, r is an integer. The obtained polymercompound is useful as the base polymer of a negative type resist.

Comparative Resin Synthesis Example 1

First, 10.0 grams of 1-adamantyl methacrylate was dissolved in 50milliliters of tetrahydrofuran and 0.5 grams of azobisisobutyronitrilewas added. After heating at 70° C. for 5 hours under reflux, theresultant solution was added dropwise to 1 liter of methanol. Theprecipitated resin was filtered off, and dried under reduced pressure toobtain a resin. The resin was a polymer compound having a monomeric unitrepresented by general formula (7) below. The yield of the resin was 8.0grams. The weight-average molecular weight (Mw) of the resin was 6,000and the degree of dispersion (Mw/Mn) was 1.5. Hereinafter, the resinwill be referred to as Comparative Resin 1.

Comparative Resin Synthesis Example 2

First, 10.0 grams of 3-hydroxy-1-adamantyl acrylate was dissolved in 50milliliters of tetrahydrofuran and further 0.5 grams ofazobisisobutyronitrile was added. After heating at 70° C. for 5 hoursunder reflux, the resultant solution was added dropwise to 1 liter ofmethanol. The precipitated resin was filtered off, and dried underreduced pressure to obtain a white powdery resin. The resin was apolymer compound having a monomeric unit represented by general formula(8) below. The yield of the resin was 8.0 grams. The weight-averagemolecular weight (Mw) of the resin was 6,100 and the degree ofdispersion (Mw/Mn) was 2.8. Hereinafter, the resin will be referred toas Comparative Resin 2.

Example 1

Measurement of Transparency (Absorption Coefficient) of Resin

Resin 1 and Comparative resin 1 were separately dissolved in toluene.Resin 2 and Comparative resin 2 were separately dissolved in propyleneglycol monomethyl ether (PGME). These four resin solutions were appliedonto magnesium fluoride wafers respectively with a final film thickness(after dry) of 0.1 micrometer. The coating films were prebaked on adirect hot plate at 130° C. for 60 seconds respectively to form fourtypes of resin films. Each of the resin films thus prepared was measuredfor transparency (absorption coefficient) to light having wavelengths of157 nanometers and 193 nanometers by vacuum ultravioletspectrophotometer (manufactured by JASCO Corporation). The results areshown in table 1.

TABLE 1 Absorption coefficient (abs/μm) 157 nm wavelength 193 nmwavelength Resin 1 2.42 0.20 Resin 2 2.66 0.21 Comparative resin 1 6.520.32 Comparative resin 2 6.91 0.31

As is apparent from Table 1, a polymer compound according to the presentinvention has quite high transparency to F₂ excimer laser light of 157nanometer wavelength, although a conventional polymer compound hardlyhas transparency. Therefore, it is found that the polymer compound issuitably used as a polymer constructing the base polymer and thedissolution suppressing agent of a resin composition of the nextgeneration.

Example 2

Evaluation of Resolution of Positive Resist Exposed to ArF Laser

Resin 3 containing 3-hydroxy-1-perfluoroadamantyl acrylate as amonomeric unit was used as a base polymer, and triphenylsulfoniumperfluorobutanesulfonate (TPS-PFBS) as an acid generating agent, andtriethanolamine as a quencher, were added in propylene glycol monomethylether acetate (PGMEA) used as a solvent, as shown below, to prepare apositive resist composition.

Resin 3 100 parts by weight Acid generating agent: TPS-PFBS 2.5 parts byweight Quencher: triethanolamine 0.2 parts by weight Solvent: PGMEA 900parts by weight

A positive resist film was formed of the positive resist composition andevaluated for resolution when ArF excimer laser light was applied. Themeasured resolution power and light exposure amount are shown in Table 2below.

Example 3

Evaluation of Resolution of Negative Resist Exposed to ArF Laser

Resin 4 containing 3-hydroxy-1-perfluoroadamantyl acrylate as amonomeric unit was used as a base polymer and triphenylsulfoniumperfluoromethanesulfonate (TPS-PFMS) and triphenylsulfoniumperfluorobutanesulfonate (TPS-PFBS) as acid generating agents, and4-phenylpyridine as a quencher, were added to propylene glycolmonomethyl ether (PGME) and pure water as a solvent as shown below, toprepare a negative resist composition.

Resin 4 100 parts by weight Acid generating agent: TPS-PFMS 1.0 part byweight Acid generating agent: TPS-PFBS 0.68 parts by weight Quencher:4-phenylpyridine 0.2 parts by weight Solvent: PGME 1,000 parts by weightPure water 80 parts by weigh

A negative resist film formed of the negative resist composition wasevaluated for resolution when ArF excimer laser light was applied. Themeasured resolution power and light exposure amount are shown in Table 2below. In Table 2, PB stands for a preparatory heating process (PreBake) performed before light exposure and PEB stands for a heatingprocess (Post Exposure Bake) performed after light exposure.

TABLE 2 Resist film PB/PEB Sensitivity thickness Temperature Resolutionto to ArF light (nm) (° C.) ArF light (nm) (mJ/cm²) Example 2 300130/130 160 18 Example 3 250 100/120 160 17

As shown in Table 2, the resist compositions according to the presentinvention containing polymer compounds of the present invention haveexcellent resolution power and sensitivity to light. It is found thatthe excellent transparency of the polymer compounds of the presentinvention used as a base polymer to ArF excimer laser light contributesto these characteristics. From this, it is obvious that the same effectscan be obtained when F₂ excimer is laser is used.

In the previous example, a polymer compound according to the presentinvention is used as the base polymer of the resist composition.However, it is also obvious that a polymer compound may be designed soas to have a small weight-average molecular weight and used as adissolution inhibitor agent optionally added to the resist composition.

INDUSTRIAL APPLICABILITY

As explained above, a polymer compound according to the presentinvention, a resist composition and a dissolution inhibitor agentcontaining the polymer compound are useful in a photoresist compositionfor the next-generation microfabrication, and particularly suitable as amaterial for forming a microfabrication pattern using F₂ excimer laserlight of 157 nanometers in wavelength.

1. A polymer compound comprising a monomeric unit derived from acrylicester or methacrylic ester having a polycyclic group at a side chain,wherein all hydrogen atoms on the ring of the polycyclic group arefluorinated and the polycyclic group has a transparency to light of 157nanometer wavelength, represented by an adsorption coefficient equal toor less than 3.0 μm⁻¹.
 2. The polymer compound according to claim 1,wherein the polycyclic group is an adamantyl group.
 3. The polymercompound according to claim 1, further comprising a second monomericunit.
 4. The polymer compound according to claim 3, wherein the secondmonomeric unit has an acid dissociable group.
 5. The polymer compoundaccording to claim 3, wherein the second monomeric group is a monomericunit derived from acrylic ester or methacrylic ester.
 6. A polymercompound comprising a monomeric unit having an alicyclic group at a sidechain, wherein more than half the number of hydrogen atoms on the ringof the alicyclic group are substituted by fluorine atoms and hastransparency to light of 157 nanometer wavelength, represented by anadsorption coefficient equal to or less than 3.0 μm⁻¹ and, wherein thealicyclic group has a hydrophilic group on a ring.
 7. A polymer compoundaccording to claim 6 wherein the alicyclic group is an adamantyl group.8. A polymer compound according to claim 6 wherein the monomeric unit isderived from an acrylic ester or a methacrylic ester.
 9. A polymercompound comprising a monomeric unit having an alicyclic group at a sidechain, wherein more than half the number of hydrogen atoms on the ringof the alicyclic group are substituted by fluorine atoms and hastransparency to light of 157 nanometer wavelength, represented by anadsorption coefficient equal to or less than 3.0 μm⁻¹ and wherein themonomeric unit is a unit derived from vinyl ether.
 10. A polymercompound comprising a monomeric unit having an alicyclic group at a sidechain, wherein more than half the number of hydrogen atoms on the ringof the alicyclic group are substituted by fluorine atoms and hastransparency to light of 157 nanometer wavelength, represented by anadsorption coefficient equal to or less than 3.0 μm⁻¹ and wherein thealicyclic group has a hydrophilic group on a ring and said polymerfurther comprising a second monomeric unit, wherein the second monomericunit has an acid insoluble group.
 11. A polymer compound comprising amonomeric unit having an alicyclic group at a side chain, wherein morethan half the number of hydrogen atoms on the ring of the alicyclicgroup are substituted by fluorine atoms and has transparency to light of157 nanometer wavelength, represented by an adsorption coefficient equalto or less than 3.0 μm⁻¹, wherein the monomeric unit is a unit derivedfrom vinyl ether and said polymer further comprising a second monomericunit, wherein the second monomeric unit has an acid insoluble group. 12.A polymer compound comprising a monomeric unit having an alicyclic groupat a side chain, wherein more than half the number of hydrogen atoms onthe ring of the alicyclic group are substituted by fluorine atoms andhas transparency to light of 157 nanometer wavelength, represented by anadsorption coefficient equal to or less than 3.0 μm⁻¹ wherein thealicyclic group has a hydrophilic group on a ring and said polymerfurther comprising a second monomeric unit wherein the second monomericunit is a monomeric unit derived from a vinylic double bond.
 13. Apolymer compound comprising a monomeric unit having an alicyclic groupat a side chain, wherein more than half the number of hydrogen atoms onthe ring of the alicyclic group are substituted by fluorine atoms andhas transparency to light of 157 nanometer wavelength, represented by anadsorption coefficient equal to or less than 3.0 μm⁻¹, wherein themonomeric unit is a unit derived from vinyl ether and said polymerfurther comprising a second monomeric unit wherein the second monomericunit is a monomeric unit derived from a vinylic double bond.
 14. Apolymer compound having a monomeric unit represented by general formula(1)

where n is an integer; X is an ester group of carboxylic acid,

ether group (—O—), —CH₂—O—, or an alkylidene group,

Z enclosed by a circle is an adamantyl group wherein more than half thenumber of hydrogen atoms on the adamantyl group are substituted byfluorine atoms; R¹, R², R³, R⁵, R⁶ and R⁷ are independently one selectedfrom the group consisting of a hydrogen atom, lower alkyl group,fluorine atom, and fluorinated lower alkyl group; 1 is an integer of 0to 3; and R⁴ is a hydroxyl group, and having transparency to light of157 nanometer wavelength represented by an adsorption coefficient equalto or less than 3.0 μm⁻¹.
 15. The polymer compound according to claim14, wherein the adamantyl group is a perfluoroadamantyl group.
 16. Aresist composition comprising a polymer compound having a monomeric unitderived from acrylic ester or methacrylic ester having a polycyclicgroup at a side chain, wherein all hydrogen atoms on the ring of thepolycyclic group are fluorinated and said polymer compound has atransparency to light of 157 nanometer wavelength, represented by anadsorption coefficient equal to or less than 3.0 μm⁻¹.
 17. The resistcomposition according to claim 16, comprising the polymer compound as abase polymer.
 18. The resist composition according to claim 16,comprising the polymer compound as a dissolution inhibitor agent.
 19. Aresist composition comprising a polymer compound having a monomeric unitrepresented by general formula (1)

where n is an integer; X is an ester group of carboxylic acid,

ether group (—O—), —CH₂—O—, or an alkylidene group,

Z enclosed by a circle is an adamantyl group wherein more than half thenumber of hydrogen atoms on the adamantyl group are substituted byfluorine atoms; R¹, R², R³, R⁵, R⁶ and R⁷ are independently one selectedfrom the group consisting of a hydrogen atom, lower alkyl group,fluorine atom, and fluorinated lower alkyl group; 1 is an integer of 0to 3; and R⁴ is a hydroxyl group; and having a transparency to light of157 nanometer wavelength represented by an adsorption coefficient equalto or less than 3.0 μm⁻¹.
 20. The resist composition according to claim19, comprising the polymer compound as a base polymer.
 21. The resistcomposition according to claim 19, comprising the polymer compound as adissolution inhibitor agent.
 22. A resist dissolution inhibitor agentcomprising a polymer compound having a monomeric unit derived fromacrylic ester or methacrylic ester having a polycyclic group at a sidechain, wherein all hydrogen atoms on the ring of the polycyclic groupare fluorinated and said polymer compound has transparency to light of157 nanometer wavelength, represented by an adsorption coefficient equalto or less than 3.0 μm⁻¹.
 23. A resist dissolution inhibitor agentcomprising a polymer compound having a monomeric unit represented bygeneral formula (1)

where n is an integer; X is an ester group of carboxylic acid,

ether group (—O—), —CH₂—O—, or an alkylidene group,

Z enclosed by a circle is an adamantyl group wherein more than half thenumber of hydrogen atoms on the adamantyl group are substituted byfluorine atoms; R¹, R², R³, R⁵, R⁶ and R⁷ are independently one selectedfrom the group consisting of a hydrogen atom, lower alkyl group,fluorine atom, and fluorinated lower alkyl group; 1 is an integer of 0to 3; and R⁴ is a hydroxyl group, and having a transparency to light of157 nanometer wavelength represented by an adsorption coefficient equalto or less than 3.0 μm⁻¹.